MacBook won't wake up from sleep mode unless I press on/off button--why not any button on keyboard? It worked in the past

Hello! These days, when my MacBook goes into sleep mode (I leave my screen up, and there's been no activity for a bit; the screen will turn black), I need to wake it up by pressing the on/off button on my keyboard. It'd wake up from sleep mode if I pushed any key or moved the mouse in the past. I haven't recently updated my MacBook or changed its settings. How can I modify this? Thanks so much!